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 Post subject: Re: Champlifier Mods
PostPosted: Thu Dec 08, 2011 11:30 am 
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A 6l6 needs 900mA of heater current. A 12ax7 needs 300ma. That adds up to 1.2A. Seems to be well within spec.
An el34 needs 1A5, so with the 12ax7 this adds up to 1A8. Pushing the envelope a bit.
Of course this generates more heat so keep on eye on things but if there's 2A there could be some octal experimenting.

This wouldn't allow for 6550 or kt88.


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 Post subject: Re: Champlifier Mods
PostPosted: Thu Dec 08, 2011 11:37 am 
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I sit corrected:
6550; 1A6


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 Post subject: Re: Champlifier Mods
PostPosted: Thu Dec 08, 2011 12:09 pm 
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I think the OT's rating of 50mADC through the primary winding might be the limiting factor...?

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 Post subject: Re: Champlifier Mods
PostPosted: Thu Dec 08, 2011 12:44 pm 
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Good question. Exceeds my knowledge.
From my readings from TUT3 as long as the PT has enough heater current then the amp should be OK. It won't produce more wattage or power just more heat and a different tone. I may be missing something though.


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 Post subject: Re: Champlifier Mods
PostPosted: Thu Dec 08, 2011 5:47 pm 
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mmarsh wrote:
What values for C2 and C3? I've noticed this behavior on my other diy champ. That one runs through a single 10" and sounds really good.


.01mfd is a good choice.

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 Post subject: Re: Champlifier Mods
PostPosted: Thu Dec 08, 2011 5:52 pm 
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defaced wrote:
Note the voltage ratings on these caps! (for the uninitiated, I know you'll know this Marsh) They will be 400v parts at minimum (the original Fender schematic calls for 600v parts, 630v is a common modern equivalent). Do not take your standard stompbox fare film caps (generally rated at 63 to 100v) and substitute them out even for testing, you will blow them up.


Yes, you certainly don't want to use a 63v or 100v. If you use the .01mfd version of the .022mfd Mallory (now Cornell Dublier) that comes with the kit, you will have to use 630v because that model doesn't come any smaller than. However, that point is only 200v, so you'd be ok with a 250v if it's all you can find. But if you have your choice, go for the larger voltage rating.

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 Post subject: Re: Champlifier Mods
PostPosted: Thu Dec 08, 2011 6:00 pm 
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defaced wrote:
That is a possibility. Having never played with these values on this amp, I defer any sonic evaluations to someone else. I have a feeling I'm going to be building one of these soon :wink:



Yes. A definite posiblity. Maybe you will like the stock values better. Personally, I don't find the bass loss noticeable. And if there is, I guess it's compensated by the larger diameter speakers that I prefer. But I think more important is the fact that the whole point of the champ, for most people, is that you can dime (or would it be dozen in this case) it and not rip your face off.

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 Post subject: Re: Champlifier Mods
PostPosted: Thu Dec 08, 2011 6:07 pm 
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byoc wrote:
But I think more important is the fact that the whole point of the champ, for most people, is that you can dime (or would it be dozen in this case) it and not rip your face off.

:lol: :lol: :lol: I only play my Champlifier dozened!

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 Post subject: Re: Champlifier Mods
PostPosted: Thu Dec 08, 2011 6:11 pm 
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Knight of Cups wrote:
If the heater current is high enough you can swap a bigger bottle tube in the power section. 6l6 el34, etc....

What is the heater amperage Keith?


Well...no. You can't do that. The heater windings are 6.3vac @ 2amps. So, yes, the heater is ok to use the big boys. But you cannot use something bigger because the OT is only rated for 6w. Maybe if you drastically changed the bias. I dunno. As it is in Class A, an EL34 would put out about 10 or 11 watts. So you'd need a bigger OT.

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 Post subject: Re: Champlifier Mods
PostPosted: Thu Dec 08, 2011 6:12 pm 
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defaced wrote:
Knight of Cups wrote:
If the heater current is high enough you can swap a bigger bottle tube in the power section. 6l6 el34, etc....

What is the heater amperage Keith?
According to the pics on the main page, the PT is a Magnetic Components 40-18019, which has 2 amps of 5v for the rectifier and 2 amps of 6.3v for everything else. Can the iron actually support a 6L6 in Class A at those voltages? Most of the stuff I'm finding online about putting 6L6s in a 5F1 start with "change the transformers"; data sheets and other Class A 6L6 designs seem to support this, but I've not personally sat down and done the load lines and don't have similar iron to experiment with.


Oops. Double post. Right. What he said.

Yes, the PT is just fine. It's the OT that you need to change. Your options are pretty limited with single ended transformers. Magnetic Components makes a 15w single ended and Hammond makes one (see the AX84 project for a part #). I'm sure there's a couple others, but I'm not familiar with them.

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 Post subject: Re: Champlifier Mods
PostPosted: Thu Dec 08, 2011 6:20 pm 
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defaced wrote:
I think the OT's rating of 50mADC through the primary winding might be the limiting factor...?


The 15w transformer can handle 70ma.

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 Post subject: Re: Champlifier Mods
PostPosted: Thu Dec 08, 2011 6:32 pm 
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FF_Pedals wrote:
I used 1k 5W. The best way to do it seems to be to move the wire from pin4 to the unused pin6 of the 6V6, then put the 1k 5W resistor from pin6 to pin4. This will really help your tube if you're overdriving it at all.


+1 on moving the wire from pin 4 to pin 6 and then running your screen resistor across 4 and 6. This is how you see most screen resistors in point-to-point amps.

I haven't tried this mod to a champ, but looking at the screen resistor(s) on most fender amps, it's a 470/1watt resistor.

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 Post subject: Re: Champlifier Mods
PostPosted: Thu Dec 08, 2011 8:17 pm 
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Did you read this Keith?
Quote:
From my readings from TUT3 as long as the PT has enough heater current then the amp should be OK. It won't produce more wattage or power just more heat and a different tone. I may be missing something though.


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 Post subject: Re: Champlifier Mods
PostPosted: Thu Dec 08, 2011 9:04 pm 
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Had to satisfy my curiosity and checked the differences between the OT that O'Connor recommends in his builds (and the one that I used in mine) and the Classictone ones. The one I have is Hammonds 125c rated @ 8W and 60maDC. The BYOC is rated 5W @50maDC. Big difference? I don't know but why take a chance.


Also, correct me if I'm wrong, but there is another primary wire so I think you could connect this Ultralinear. Basically you'd connect the brown wire to the screen (pin 4)
This is very unverified as this is just a hunch by me but it is certainly something to look into.
It is said that if you take away NFB that connecting the screen UL will sound great. And you could always switch between the two.


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 Post subject: Re: Champlifier Mods
PostPosted: Thu Dec 08, 2011 10:27 pm 
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Knight of Cups wrote:
Also, correct me if I'm wrong, but there is another primary wire so I think you could connect this Ultralinear. Basically you'd connect the brown wire to the screen (pin 4)
This is very unverified as this is just a hunch by me but it is certainly something to look into.
It is said that if you take away NFB that connecting the screen UL will sound great. And you could always switch between the two.

That sounds really cool! I'd like to explore that more.

My 5E1 clone has a Hammond OT in it. I probably have about 100 hours running a 6L6 in it with no issues.

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 Post subject: Re: Champlifier Mods
PostPosted: Fri Dec 09, 2011 11:23 am 
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Edcor has 25W output transformers: http://www.edcorusa.com/category/68-xse ... wattage=40


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 Post subject: Re: Champlifier Mods
PostPosted: Fri Dec 09, 2011 11:31 am 
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Can't help smiling to myself here--traditionally, the key selling point to the Champ is it's low power output and the ability to generate output tube overdrive at volumes that don't make your ears bleed. So naturally, one of the first modifications we talk about is how to pump up the output power! :roll:

So how big of an OT am I gonna need to run a KT120 in this thing? :wink: :lol:

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 Post subject: Re: Champlifier Mods
PostPosted: Fri Dec 09, 2011 11:38 am 
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It's not to get more power it's more for tube tasting.


Also it's pretty easy to do a pentode triode switch (harder to do is make a hole in the chassis for it)
Pin 4 is your screen - normally wired it's in pentode - to wire it triode you'd have to share the plate wire (from pin 3)this changes the impedance of the tube and cuts output to half.

I have to say though that I did this to my "Champ" and it was really hummy and I was generally underwhelmed YMMV.


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 Post subject: Re: Champlifier Mods
PostPosted: Fri Dec 09, 2011 11:59 am 
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Knight of Cups wrote:
It's not to get more power it's more for tube tasting.

Yep. I like the way a 6L6 distorts better in a Champ. Sounds more like a 'grown up' amp, but at a non-grown up volume. :wink:

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 Post subject: Re: Champlifier Mods
PostPosted: Fri Dec 09, 2011 4:32 pm 
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Knight of Cups wrote:
Did you read this Keith?
Quote:
From my readings from TUT3 as long as the PT has enough heater current then the amp should be OK. It won't produce more wattage or power just more heat and a different tone. I may be missing something though.


No. I missed that. Huh? Morgan says he's gonna try it, so I reckon we'll find out.

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 Post subject: Re: Champlifier Mods
PostPosted: Fri Dec 09, 2011 4:33 pm 
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Morgan wrote:
Knight of Cups wrote:
It's not to get more power it's more for tube tasting.

Yep. I like the way a 6L6 distorts better in a Champ. Sounds more like a 'grown up' amp, but at a non-grown up volume. :wink:


Oh. Looks like he did already!

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 Post subject: Re: Champlifier Mods
PostPosted: Fri Dec 09, 2011 6:42 pm 
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byoc wrote:
Morgan wrote:
Knight of Cups wrote:
It's not to get more power it's more for tube tasting.

Yep. I like the way a 6L6 distorts better in a Champ. Sounds more like a 'grown up' amp, but at a non-grown up volume. :wink:


Oh. Looks like he did already!

Well...I've done it on my old clone with the Hammond OT. I'm going to try it with the BYOC one too just to see how the OT does.

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 Post subject: Re: Champlifier Mods
PostPosted: Fri Dec 09, 2011 7:29 pm 
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Just to be scientific about it take plate and cathode voltages with both tube types.

Quote:
I'm going to try it with the BYOC one too just to see how the OT does


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 Post subject: Re: Champlifier Mods
PostPosted: Tue Dec 13, 2011 12:01 am 
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Just throwing this out there. The new Fender EC Vibro-Champ is also based on the 5F1 circuit. Has an output tube bias tremolo, "attenuator" switch to reduce output, and a bias pot inside. Controls include On/Off Switch, Attenuator Switch, Volume, Tremolo Speed. Jewel light between power and attenuator switches. Tubes are 6V6, 5Y3, and a pair of 12AX7s. There's also a Tremolo Footswitch Jack.

How viable would it be to add features like these to this Champ clone as a series of mods?? It's understood that there are challenges with the control layout on the chassis, and also the need for another 12AX7 socket and other bits of hardware.

Cheers...
Erik


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 Post subject: Re: Champlifier Mods
PostPosted: Tue Dec 13, 2011 9:41 am 
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It's certainly possible. But like you said, the toughest part would be punching another 12ax7 hole into the chassis. You'd also have to use another turret board as you couldn't use the one provided. It would be cool to have an option of no chassis with purchase.


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